WARNING: This video, shot by the advocacy group Mercy for Animals at a farm in Oklahoma, includes graphic and sometimes bloody scenes. It shows pigs being kicked, hit, and thrown, as well as pigs being slammed into the floor to kill them.

By Anna Schecter, NBC News

The nation’s largest meat producer has announced new animal care guidelines for its pork suppliers a month and a half after NBC News showed the company undercover video of workers on one of its farms kicking and hitting pigs and slamming piglets into the ground.

On Wednesday, Tyson Foods sent a letter to suppliers requiring that some farms stop using blunt force euthanasia to kill piglets and urging that all its suppliers keep sows in larger cages, install video cameras in sow farms, and adopt “pain mitigation” methods when castrating piglets or docking their tails.

In its letter, Tyson said it recognized that killing piglets with blunt force “has been historically acceptable” to the meat industry, “but may not match the expectations of today’s customers or consumers.”

“We’re trying to balance the expectations of consumers with the realities of today’s hog farming business,” said the letter, which was signed by a senior vice president and the vice president who runs the company’s Animal Well-Being Programs. “We look forward to working with you on our current challenges.”

Though the letter encourages all suppliers to adopt a different form of euthanasia, its order to end blunt force euthanasia applies only to contract farms, meaning farms where Tyson owns the animals and the farm owner supplies meat to the company under contract. All other guidelines in the letter are recommendations.

The head of the animal rights group that shot the undercover video applauded the company’s change in policy. "It’s heartening that Tyson has finally begun to address the rampant and horrific cruelty uncovered at its factory farm facilities by Mercy For Animals," said Nathan Runkle, executive director of the group.

Mercy for Animals

Undercover video shot by the advocacy group Mercy for Animals at West Coast Farms in Henryetta, Okla., allegedly shows workers hitting, throwing and kicking pigs.

“The announcement that Tyson is making significant animal welfare improvements, including urging its pork producers to move away from inherently cruel and restrictive gestation crates, signals an important new era and direction for the company,” said Runkle. “We urge Tyson to add more teeth to the new guidelines by making them a mandate for all of its pork producers, rather than a mere recommendation.”

Gestation crates are metal enclosures two feet wide and six-and-a-half feet long widely used by pig farmers to house sows during pregnancy. Gary Mickelson, director of public relations for Tyson Foods, said the company had “tried to make it clear that we have not taken a position against any particular type of sow housing, including gestation stalls.” Asked whether the new set of animal care policies was spurred by the MFA video, he said the timing “was not due to any one incident or organization.”

In November, Tyson Foods terminated its contract with West Coast Farms of Okfuskee County, Okla., after NBC showed the company video shot by an activist from Mercy for Animals. The activist worked undercover as a farmhand from mid-September to mid-October.

The undercover worker who shot the video, “Pete,” told NBC News that abuse was “commonplace and constant” at West Coast Farms. He said that it included hitting, kicking, throwing, striking animals with the edges of wooden boards, sticking fingers in their eyes, and leaving piglets to die slowly after they were slammed into the ground “in failed euthanasia attempts.” According to Pete, some of the piglets were alive 30 minutes after being slammed into the ground.

The owner of the farm said that the video showed "mistreatment" of animals and said he had taken action of his own. “I was stunned that anyone could be that callous in their treatment of any animal," said Lonnie Herring. "After viewing the video, I immediately returned to my farm and terminated the employees seen in the video."

Herring also said that his farm used approved methods of euthanasia on animals, and that the animals were euthanized in a humane fashion. He also said his workers were “trained and instructed” that they must verify an animal is dead “before [they] leave that animal.”

“It is a part of the business and there are prescribed methods of euthanasia and I follow those to a T,” said Herring.

Tyson Foods owned the sows and boars on the farm, while Herring owns the farm itself and provided meat to Tyson under contract.